North Castle Wastewater Treatment Plant

Town of North Castle
Westchester County, NY

The Town of North Castle commissioned a project to upgrade the existing North Castle Sewer District No. 2 Wastewater Treatment Plant (WWTP) to enhance operations and create further efficiencies in complying with nitrogen limits. EDR was retained by the Town to provide the planning, engineering, and environmental services for the project which includes the following primary elements:

  • Granular Activated Carbon (GAC) adsorption system to enhance further reduce nitrogen in the denitrification filter effluent
  • Ultraviolet (UV) disinfection
  • Mechanical sludge thickening – ability to increase sludge throughput
  • Plant water reuse
  • Pump control panel replacements

The facility’s most recent plant upgrade was completed in 2009, which was the implementation of nitrogen removal upgrades. These improvements were necessitated since the wastewater facility is part of the Long Island Sound Management Zone 7. A pilot study completed in 2015 indicated that the use of GAC filters downstream of the existing denitrification filters improved nitrogen removal by a significant margin. An increase in efficiencies and improved nitrogen removal is needed for maintenance issues when a treatment tank is taken out of service. The project includes multiple Granular Activated Carbon vessels to further remove nitrogen from denitrified effluent. The vessels are arranged with automated valving to provide the flexibility in operating them in a series or parallel configuration. The vessels and two new ultraviolet units are housed in a prefabricated building located in an area previously utilized for sludge drying. The sludge thickener is being replaced with a large unit to reduce operations by 40-60%. In conjunction, denitrified effluent will be utilized as the washwater source for the sludge thickener. This will result in a significant reduction in potable water usage and expense for the plant. The pump control upgrades will replace three panels to convert each to a PLC-based type to align with and communicate with the Plant SCADA system.